None.
This invention relates generally to hand-held firearms, and particularly concerns both apparatus and methods for precisely aligning the vertical cross hair of the reticle system of an attached sighting scope to be parallel to a symmetry axis of the firearm that is vertical and perpendicular to the firearm bore.
Sighting scopes, both those that magnify the sight field and those which have reticles but do not magnify the sight field, are typically mounted on their respective rifle, pistol, or shotgun by means of co-operating mounting rings attached to the receiver of the firearm. The scopes contain reticles which are a system of lines, dots, cross hairs, wires, or electrically projected images which aid in the sighting of a target and proper positioning the weapon relative to a target. A common reticle system is comprised of a horizontal cross hair intersected by a vertical cross hair.
It has been found that most times when a scope is mounted in the scope mounting rings attached to the receiver area of the firearm the scope is canted or rotated to some degree such that the vertical cross hair of the reticle system is not positioned parallel to the vertical axis of the firearm and does not necessarily intersect the longitudinal axis of the firearm bore. Shooters, especially competition target shooters, tend to compensate for the included cross hair canting by counter-rotating the firearm and thus compromise the accuracy of this shot.
It has been discovered that by aligning the vertical cross hair of the reticle system with the vertical axis of the firearm the accuracy of the firearm is noticeably improved.
The present invention is essentially comprised of a vertical reference shaft sub-assembly and a co-operating firearm level sub-assembly that is removably attached to the receiver area of the firearm. The vertical reference shaft sub-assembly is further comprised of a weighted base member, a mounted vertical reference shaft, and a bubble level mounted at the top of the vertical reference shaft and oriented perpendicular to the axis of the shaft. Such sub-assembly is completed by the inclusion of leveling screws mounted on the weighted base member.
The co-operating firearm level sub-assembly is comprised of an elongated rigid bar member having a flat undersurface and a bubble level mounted at the end of the rigid bar member away from the flat undersurface and oriented parallel to the longitudinal axis of that bar member. The level sub-assembly also includes an elastic band which functions to removably mount the sub-assembly upon a firearm with the sub-assembly flat undersurface contacting and being supported by an upper surface of the receiver area of the firearm.
From a method standpoint the invention involves the steps of positioning the firearm having a scope with a canted reticle system so that its vertical axis is positioned vertically as indicated by the level bubble of the mounted level sub-assembly, positioning the vertical reference shaft sub-assembly a distance from the muzzle end of the firearm, then rotating the scope on the firearm sufficiently to align the vertical cross hair of the scope reticle system with the distant vertical reference shaft sub-assembly, and lastly locking the sighting scope in the corrected position on the firearm.